1. Field of the Invention
The present invention relates to an attachment for preventing liquid from adhering to an electronic component, in particular, to an attachment for preventing liquid from adhering to an electronic component which is mounted on an electronic substrate of a motor drive unit.
2. Description of the Related Art
In the prior art, various means for preventing liquid from adhering to an electronic component have been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 2001-185866 discloses an electronic device attached to an interior attachment surface such as a wall surface or a window frame, wherein the device has a drip-proof structure having an upper edge adhered to the attachment surface and a chute for guiding water drops.
On the other hand, a structure for preventing liquid from adhering to an electronic device used in a numerical controller, etc., has been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 2007-048946 discloses a casing of an electronic device containing an electronic substrate and a fan motor for cooling an electronic component mounted on the substrate, wherein a lower surface of an upper part of the casing attached to the fan motor is formed as an inclined surface so that water or oil accumulated in a housing of the fan motor flows as a droplet along the inclined surface, in order to prevent the droplet from adhering to the electronic component.
In the drip-proof structure of Japanese Unexamined Patent Publication (Kokai) No. 2001-185866, a water drop is prevented from adhering to the electronic component attached to the wall surface or the window frame. However, the drip-proof structure can prevent a water drop, which flows on the wall surface or the window frame only, from adhering to the electronic component. Therefore, in the drip-proof structure of Japanese Unexamined Patent Publication (Kokai) No. 2001-185866, it is difficult to prevent a water drop, which scatters from a portion other than the wall surface or the window frame, from adhering to the electronic component.
In contrast, in Japanese Unexamined Patent Publication (Kokai) No. 2007-048946, the casing structure is effective in protecting the electronic component from water droplets which are moved from the fan motor, etc. However, it is necessary to previously form the casing structure so as to have a special shape such as having inclined surface, etc. Therefore, it is necessary to prepare different casing structures for use, depending on whether the drip-proof property is required or not, which is disadvantageous in terms of parts management and cost.